Occurrence of Ultrashort-Chain Per- and Polyfluoroalkyl Substances in the Coral Reef Ecosystem of the Beibu Gulf, South China Sea

Ultrashort-chain per- and polyfluoroalkyl substances (USC-PFAS) have gained increasing attention due to their ubiquitous environmental presence and escalating environmental concerns. However, data on their presence in corals remain lacking. This study investigated the concentrations of USC-PFAS, including trifluoroacetic acid (TFA), perfluoropropionic acid (PFPrA), trifluoromethanesulfonate (TFMS), perfluoroethanesulfonate (PFEtS), perfluoropropanesulfonate (PFPrS), and bisperfluoromethane sulfonimide (bis-FMeSI), along with other legacy and emerging PFAS in reef-building coral samples (n = 54) from the Beibu Gulf of the South China Sea. Among the USC-PFAS, TFA, PFPrA, and bis-FMeSI exhibited detection rates of 100%, 74%, and 72%, respectively, in coral samples. TFA dominated the PFAS profile, accounting for 86% of the total concentrations by weight, with concentrations (median: 23 ng/g dw) far exceeding those of all other legacy and emerging PFAS. The wet-weight-based logarithm bioaccumulation factors (log10 BAFs) from seawater to coral were estimated to be 1.85–3.60 for TFA, 2.07–4.09 for PFPrA, and 0.56–3.43 for bis-FMeSI, suggesting their bioaccumulative potential in reef-building corals. This study provides the first evidence of the widespread occurrence of USC-PFAS, particularly TFA, in reef-building corals, underscoring the need for further research into their potential ecological risks.